Review: evidence does not support use of static magnets for pain
M H Pittler
Dr M H Pittler, Peninsula Medical School, Exeter, UK;
Medline, CINAHL, EMBASE/Excerpta Medica, Allied and Complementary Medicine Database, Scopus, Cochrane Library, and UK National Research Register (to March 2007); conference proceedings (1996–2006) and selected journals (1994–2006) on alternative and complementary medicine; reference lists; and the authors’ collections of articles.
Study selection and assessment:
randomised controlled trials (RCTs) that compared static (permanent) magnets with placebo or a device with weak magnetic field strength for treatment of pain related to any condition. 25 RCTs (n = 1582, range of mean ages 19–65 y) met the selection criteria. 4 RCTs involved patients with joint pain from osteoarthritis, and 3 RCTs each involved patients with low-back pain, delayed-onset muscle soreness, and foot pain. The other RCTs assessed pain related to various conditions. Duration of trials ranged from 30 min to 26 weeks. Quality assessment of individual trials was done using the Jadad scale and the Cochrane classification of allocation concealment. All but 2 RCTs were double-blinded.
change in pain from baseline.
Meta-analysis of 9 randomised placebo-controlled trials that assessed pain on a 100 mm visual analogue scale showed differences in pain reduction ranging from −4 to 12 mm. When these results were pooled, there was no difference between groups (table). Meta-analysis of 16 RCTs (including the 9 mentioned above) that used various scales for assessing pain showed a benefit for magnets; however, significant statistical heterogeneity was present. 3 of 4 trials of osteoarthritis (total n = 275) and 1 of 3 trials of low-back pain (total n = 146) reported that magnets reduced pain more than placebo or weak magnets, but 3 trials of delayed-onset muscle soreness (total n = 88) and 3 trials of foot pain (total n = 224) found no difference between groups.
Evidence does not support the use of static magnets for pain relief. More evidence is required to determine whether magnets reduce joint pain from osteoarthritis.
Pittler MH, Brown EM, Ernst E. Static magnets for reducing pain: systematic review and meta-analysis of randomized trials. CMAJ 2007;177:736–42.
Clinical impact ratings: Complementary care 6/7; Family/General practice 4/7; Pain management 6/7
The meta-analysis by Pittler et al used a robust and widely accepted method to evaluate a limited number of acceptable RCTs. The authors concluded that, methodologically, all included RCTs had flaws, and in some cases, it was inappropriate to pool results because differences in data-gathering tools were too large. This second point is an important issue for designers of chronic pain trials and has led for a call to standardise research to avoid this problem in future.1
Pooled results showed that reductions in visual analogue scale scores were statistically non-significant. This finding means that it is impossible to recommend static magnet therapy for pain relief in general; this position was also adopted by an earlier commentary in Evid Based Nurs.2
Pittler et al found inconclusive evidence of a small benefit for peripheral joint osteoarthritis. They suggested several ways in which magnet therapy research could be improved; however, because any effects are likely to be small, allocation of resources to investigate this treatment is questionable.
The bottom line is that magnet therapy is a popular and widely promoted technique that has no merit as a method of pain relief. It can be argued that there is no harm done to patients who use magnets, and they may derive other benefits, such as feeling some level of control. Although physical harm might not be an issue, the negative findings of this review should lead nurses to advise patients with chronic pain to avoid spending money on static magnets.